1. Field of the Invention
This invention relates to stents of improved cell configuration.
2. Brief Description of the Prior Art
Stents are radially expandable endoprostheses which are typically intravascular implants capable of being implanted transluminally and enlarged radially after being introduced percutaneously. They have also been implanted in urinary tracts and bile ducts. They are used to reinforce body vessels and to prevent restenosis following angioplasty in the vascular system. They may be self-expanding or expanded by an internal radial force, such as when mounted on a balloon.
In the past, stents have been generally tubular but have been composed of many cell configurations and have been made of many materials, including metals and plastic. Ordinary metals such as stainless steel have been used as have shape memory metals such as Nitinol and the like. Stents have also been made of biodegradable plastic materials. Such stents have been formed from wire, tube stock, and the like.
This invention provides new configurations of the cells making up stents which may be adapted to all of the various types of prior art stents described above and/or known previously in the art. In general, as will be seen from the embodiments described hereinafter, the improved cell configurations are generally trichotomous, i.e., divided into three parts. More particularly, the cells are of a triskelion-like or trifurcate configuration, i.e., composed of three parts with axes of each part radiating from a common center. There are numerous advantages to the new configurations. For example, the configurations of the invention limit recoil and add resistance to compression for an expanded stent and provides increased side branch access, among other things. Also, the stents of this invention are longitudinally flexible.
The invention is also directed to a stent of generally cylindrical shape composed of at least one multibonate cell structure and desirably of a plurality of interconnected multibonate cell structures, as defined below. The multibonate structures may be interlocking and may be regularly arranged.
The invention contemplates stents having only one type of multibonate cell structure present as well as stents having a plurality of different multibonate cell structures present. Stents comprised of a plurality of multibonate cell structures of different order are also contemplated.
The invention is also directed to a stent comprised of a plurality of interlocking cell structures selected from the group consisting of bonate cell structures oriented at an oblique angle relative to the longitudinal axis of the stent, multibonate cell structures and combinations thereof.